txt NL Why “the softest” among the great climat crisisis, which return every 2,400 years, when 2,400-year oceanic cycle reaches its maximum, during the last interglacial epoch was the one that occurred ca. 400 AD.
This exclusive “softness” of the last great climat crisis is explained by the certain coincedence of the Earth axis precession прецесії and phases of the annual Earth motion along its elliptic orbit. Now more details about it.
Let us remind that period of the Earth axis precession, i.e. its uniform revolution in perpendicular to the plane of the Earth orbit clockwise, if the ecliptic plane is watched from the Earth North pole, is ca. 25,729 years, i.e. angular velocity of precession is about 50``per annum or 1° per 72 years. - *Пр26.39, 18*.
Now the Earth passes perihelion (the closest to the Sun point of the elliptic Earth orbit) in the first 10 days of january, while aphelion (the most distant point) – in the first 10 days of July, i.e. approximately 12-14 days after summer and winter solstice respectively in the southern hemisphere. Note that we consider the southern hemisphere because it bears the greater part of the oceanic mass, the principal receptor and accumulator of heat energy that comes to the Earth from the Sun, that is why mean temperature of the World ocean is the principal parameter among those that determine the state of the global climate.
So, approximately 1,000 ago the Earth passed perihelion ca. December 22, at the summer solstice in the Southern hemisphere. This means that 1,000 ago, when the Southern hemisphere was maximally turned to the Sun, then the Earth itself was in the closest to the Sun point, while in winter, when the Southern hemisphere was maximally turned from the Sun, the Sun – Earth distance was the greatest. It used to lead to the fact that thr annual insolation regime of the Southern hemisphere was maximally contrast, in this, in its turn was the cause of the least intensive heating of the oceanic mass (at fixed level of solar activity). And this is because.
According to the thermodynamics laws, backward radiation of a body, which periodically receives equal portion of energy, is higher, the higher is contrast of such energy distribution during a single period. It is a corollary, in particular, of the formula, which is a result of the simplest linear-regressive modelling process of the Earth surface radiation based on the Stephen-Bolzman law. This formula sets the dependence of the flow of Earth surface radiation W on its absolute temperature Т, and is as follows:
W = C1*k*(T degree4) - C2 ,
where k - Stephen-Bolzman constant, and C1 , C2 are the regression factors, which model the atmospheric counterradiation (addend - C2) and its transparency for direct radiation (factor C1) - *Пр26.31.2, 95-96*. Due to the radiation flow is proportional to the fourth power of the temperature, the dependence of radiation on temperature is sharply concave function.
The latter explains the fact that under hoter summer and colder winter in the Southern hemisphere the ocean returns back to the outer space much greater hart of the annual portion of energy received from the Sun, than under the condition of smoother jumps of temperature during solar year.
So, approximately 1,000 years ago relationship of the phases of precession and annual orbital movement of the Earth was such, that provided the most intensive overradiation of heat energy by the ocean surface, directed back to outer space. Among the three maximums of 2,400-year oceanic cycle (ca 2,000 BC, 400 AD, 2,800 AD) this extremal coincedence is in time the closest to the maximum, which occurred ca 400 AD. That is why it was softer than the previous one and the one which will take place in approximately 800 years.
Literature
Pr26.39. Mercurio Ed. The effects of galactic cosmis rays on weather and climate on multiple time scales. - Internet-publication. - Hartnell College. - September, 2002.
Пр26.31.2. Хауз Ф.Б. (House F.B.) Эмпирическая модель реакции атмосферы на астрономические вариации инсоляции. // Solar-Terrestrial Influences on Weather and Climate. - Proceedings of a Symposium. The Ohio State University. 1978. // Русский перевод: Солнечно-земные связи, погода, климат. - “Мир”. М., 1982.С.95-101.
Translated by Victor Tarasjuk.